Precision Electrochemical Fabrication of Corrugated Waveguides

The development of future particle accelerator technology necessitates the generation of high-power radio frequency waves, which can be achieved via power extraction into a waveguide. To advance towards higher than conventional frequency ranges (e.g. 30 – 300 GHz), metal waveguides with small features (dimensions of millimeter to sub-millimeter) such as corrugations are required. Fabrication of these features remains a challenge – especially considering the waveguide material properties as well as length scale and aspect ratio requirements. This program will demonstrate and develop a sophisticated electroforming process for fabrication of oxygen-free (high-purity) corrugated copper cylindrical waveguides. The innovative approach leverages a pulse-modulated electroforming process that employs an additive-free electrolyte bath and enables selective control of ions throughout electrodeposition. The additive-free bath limits the incorporation of impurities and thus, promotes high- purity waveguides. The selective control of ionic transport facilitates conformal and trench-filling deposits on the mandrel that correspond to well-defined and reproducible corrugation features on the waveguide. Phase I will demonstrate an innovative, additive-free, electroforming process towards achieving corrugations on copper. An appropriate metal mandrel containing corrugations will be employed and optimized as the substrate for subsequent electroforming of copper. After mandrel separation, the copper electroform will be characterized to ensure the appropriate corrugation features have been transferred. The replication quality will be quantified by comparing the arithmetic average surface roughness of the mandrel with the electroform as well as examining representative cross-sectional regions of the electroform for keyhole voids or other non-uniformities. Successful implementation of this technology would result in the reliable, reproducible, and economic production of oxygen-free copper waveguides with internal corrugation features enabling and advancing microwave technology for the generation, amplification, and/or transmission of higher than conventional frequencies (e.g. 30 GHz – 300 GHz), electron accelerators for beam manipulation, and novel wakefield accelerators. This technology could result in additional advancements towards even higher frequencies to benefit military, commercial, and civilian telecommunications, plasma diagnostics and heating of fusion plasmas (fusion energy reactors), and spectroscopic identification and imaging in security and medicine. More generally, the successful demonstration of pulsed electroforming technology would improve precision fabrication of miniaturized features and components for general consumer and commercial applications including micro-filtration, micro-optics, recordable media, sensors, injection/print nozzles, medical stents, and micro-motors.